\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}
	\begin{axis}
		[symbolic y coords={a small bar,a medium bar,a large bar},
			ytick=data,
			xbar,
			y=0.7cm,
			enlarge y limits={abs=0.5cm},
		]
		\addplot[fill=blue] coordinates
			{(42,a small bar)
				(50,a medium bar)
				(80,a large bar)
			};
	\end{axis}
\end{tikzpicture}
\end{document}
